During civilian safety missions of rescue type such as human recovery on a road after an accident, helicopters operate in an isolated spot without any precise landmark for pinpointing the site of operations, for example an injured person in a field where the only given landmarks are the names of the villages in the vicinity. The problem faced by the pilot in missions of this kind is to be able to easily obtain a fix on his location permanently with respect to surrounding features since he does not have the precise position of the site of operations. This is so, whether it be during the flight, where the pilot seeks to ascertain his location permanently with respect to the vicinity, for example to know which village it is that he spots from afar (knowing that all the small villages in the region may resemble one another) or at the end of the flight on approaching the final destination, where the pilot seeks characteristic features allowing him to better ascertain his location with respect to the site of the accident.
The problem is rendered complex during these missions by the fact that all these locating actions must be performed while ensuring flight safety and compliance with flight regulations, notably the permitted minimum altitude for overflying a village. Now, this locating is rendered difficult by the fact that it takes place in an isolated spot, accentuated by the fact that the people on the ground may have few visual features for indicating to the helicopter where they are. This difficulty of locating is all the more acute when operations proceed under unfavourable weather conditions, since visual locating is a compulsory step in this type of mission.
Today, the helicopters used for these missions are helicopters equipped with sophisticated flight assistance devices. However, their equipment does not make it possible to solve the aforementioned problems in respect of missions of such a type. Indeed, the content and the precision of their database, their information display zooms, their system waypoints, are optimized for missions of long distance type under instrument flight rules. However, no precise databases of the site being searched for exist when dealing with local missions, and pilots do not have useful information for getting to the right spot, for identifying it dependably and for putting down correctly. Therefore, when they locate a small village, it is hard for them to know whether it is the destination village or the neighbouring village. As an aid to help them get a fix on their location, pilots often use NGI (National Geographic Institute) paper maps of the region initially provided for use in cars and/or by ramblers. They locate secondary roads (across counties for example), railway tracks, streams and other characteristic features close to the villages being searched for (cemeteries, water towers for example).
Moreover, the use of a satellite navigation device (GPS for “Global Positioning System”) would only partly solve the problem, since in isolated areas, situated between two villages for example, the GPS device does not allow a location fix to be obtained readily.
These difficulties require several sources of information in order to be certain, this taking time, of the fuel required in conditions of visibility “at the permitted limits”. This search is all the longer as the pilot must in parallel continue to pilot manually, to monitor the fuel, the local weather and potentially dangerous obstacles, all at low altitude. Now, a helicopter's range for this type of mission is often reduced, and the success of the mission thus depends on the pilot's swiftness in reaching the site of operations. These difficulties sometimes involve mission cancellations, in as much as the pilot experiences difficulties in obtaining a fix on his location, in putting down and in returning to base with limited fuel reserves.
Other problems specific to aeronautics come into play for which the GPS device does not offer any effective solution and may even be a disturbing element in relation to the management of these problems by overly attracting the pilot's attention. Fuel management is paramount in order to know whether the fuel level is sufficient to get to the site of operations and to return to the departure base. Regulations demand that a reserve of 20 flying minutes be conserved for example. Moreover for these missions, the fuel given is often limited and the pilot has little margin for manoeuvre in his mission.
Weather management is difficult to ensure at the same time as the piloting and locating tasks. The crew must comply with a maximum speed which is dependent on the visibility distance. The worse the visibility, the lower the speed of translation and as a direct consequence the larger the drift due to the wind. In a phase of putting down in a field, the orientation of the wind with respect to the helicopter is very important.
The management of obstacles is specific to helicopters which fly at low altitude and therefore very exposed to electrical lines and to isolated obstacles for example. Moreover account must be taken of obstacles in front and behind (travelling backwards being another specific feature of helicopters). This management is very important in a low altitude recognition phase just before putting down in a field with a severe time constraint when a serious injury is awaiting attention.
The management of regulations is also a problem to be taken into account, notably the regulatory altitude to be complied with in the case of overflying a district. This overfly altitude depends on the extent of the district in question.